One of the features of UNIX-like operating systems is process address space protection. Basically, all applications (i.e., processes) run in their own address space and any attempt made by an application to access address space that does not belong to the application (i.e., a memory-address violation) results in abnormal termination of the application. Abnormal termination of an application may also result from an illegal instruction, a bus error, or a user-generated quit signal. Upon the abnormal termination of an application, a device within the kernel of the operating system causes process state information to be written or “dumped” to a local permanent storage device. The file that is written to the local permanent storage device is typically named “core” or “<programname>.core” and is generally referred to as the “core file” or just the “core.” The process of saving the core file to a local permanent storage device is often referred to as a “core dump” or a “crash dump.”
In prior art operating systems, the kernel of the operating system includes a core dump device that generates the core file and stores the core file in the local permanent storage device. The core dump device may store the core file in flash memory, a hard disk, or a removable storage device. Having the core file generated by the kernel and relying on the kernel to store the core file in a local permanent storage device works well in systems where there is plenty of local storage capacity available. However, in many computer systems such as networking equipment (e.g., routers and switches), embedded systems (e.g., bioelectronic devices, telephone voice switches, aircraft controllers), and appliances (e.g., robots, mobile communications devices), local permanent storage capacity is limited. In particular, many such systems do not have enough flash memory capacity or a large local storage device such as a hard disk or removable storage media that can be used to store the core file. Although the permanent storage capacity in these types of computer systems is limited, it is still desirable to be able to generate and save a core file so that application crashes can be debugged.
In view of this, what is needed is a technique for managing process state information that is flexible and that can be applied to computer systems with limited local storage capacity.